10203609597domain: NAppears in sequencesa(n) = Sum_{k=0..floor(n/3)} binomial(2*n-3*k, n).at n=18A105872a(n) = Sum_{i=0..floor(q(n)/3)} binomial(n-3*(i+1), q(n)-3*i) with q(n) = ceiling((n-3)/2).at n=36A366107